1. Field of the Invention
The invention relates to a vehicular control apparatus and control method. More particularly, the invention relates to a vehicular control apparatus and control method that executes shift control of an automatic transmission.
2. Description of the Related Art
One known vehicular control apparatus performs shift control of an automatic transmission that has an automatic shift mode (hereinafter referred to as “automatic mode”) in which the gear of the automatic transmission is selected automatically based on the vehicle speed and the throttle opening amount, and a manual shift mode (hereinafter referred to as “manual mode”) in which a driver can manually select the range by operating a shift lever. The control apparatus performs the shift control of the automatic transmission by switching between these two modes, (i.e., the automatic mode and the manual mode) according to an operation by the driver. Having the vehicular control apparatus normally control the automatic transmission in the automatic mode makes driving easier by eliminating the need for the driver to perform shift operations. On the other hand, because in the manual mode the vehicular control apparatus controls the automatic transmission based on an operation of a shift lever by the driver, the manual mode enables the driver to dictate the running state of the vehicle to achieve faster acceleration of the vehicle or increased braking force using the engine brake, for example.
Japanese Patent Application Publication No. 8-312774 (JP-A-8-312774) describes one such example of a vehicular control apparatus that reduces the load on an internal combustion engine when it has been continually high for a predetermined period of time or longer (i.e., that brings the engine out of a high load state when the engine has continued to be in the high load state for a predetermined period of time or longer) in the manual mode by forcing the automatic transmission to upshift.
The related vehicular control apparatus described in JP-A-8-312774 includes a manual mode detecting unit that detects when a gear of the automatic transmission is specified in the manual mode, a high load state detecting unit that detects whether the engine is in a high load state, a timer unit that measures the time during which the engine is in the high load state, and a forced upshift executing unit that forces the automatic transmission to upshift into a higher gear.
With this kind of a related vehicular control apparatus, when the manual mode detecting unit detects that the automatic transmission is in the manual mode, the high load state detecting unit detects that the engine is in a high load state, and engine has been in the high load state for a predetermined period of time or longer as measured by the timer unit, the forced upshift executing unit forces the automatic transmission to upshift into a higher gear. This prevents the various elements in the automatic transmission and the engine from overheating, thus improving durability, when the driver has been running the vehicle in a low gear in the manual mode for an extended period of time.
However, with the related vehicular control apparatus, an upshift is forcibly performed when the engine continues to be operated in a high load state for a predetermined period of time or longer while the vehicle is running in the manual mode. As a result, when the driver wishes to decelerate using the engine brake and thus releases the accelerator, the braking force from the engine brake is reduced, forcing the driver to operate the brakes unexpectedly, which reduces the stability of the vehicle while running.